world cancer report - iarc

Fig. 5.14 Physician reading digital images of the
breast in preparation for a computer-guided minimally
invasive biopsy.
some parts of South America, especially
Uruguay and Argentina. In contrast, low
rates are found among African and Asian
populations. Amongst population-based
cancer registries (as distinct from national
estimates), the 30 recording the highest
rates include 20 registries from North
America, one from South America (Montevideo),
two from Israel and five from
Europe. Amongst this group, the only one
from Africa is for Europeans in Harare. By
contrast, among population-based registries
with the 30 lowest rates, five are
from Africa, 18 from Asia and Israel, three
from South America, two from Eastern
Europe and two from the United States of
America (American Indians in New Mexico
and Koreans in Los Angeles, California)
[2].
These large geographical differences are
potentially explicable on the basis of
genetics or the influences of lifestyle and
environment. Studies of migrant populations
have revealed that when women
migrate from low-risk to high-risk regions,
the migrant populations acquire the rates
of the host country after two or three generations,
indicating lifestyle as primarily
determining the geographic variations in
risk.
“Cumulative incidence” represents the
probability of developing a particular disease
over a life span. Given the uncertainties
of breast cancer diagnosis in older
women and the high likelihood of the disease
not being reported in the oldest age
groups, it is common practice to present
cumulative incidence for the age span 0-
74 years. In the world, cumulative inci-
dences for breast cancer vary from 0.76%
for women in Kangwha, Korea to 11.9% for
non-Hispanic whites in San Francisco,
USA [2].
The absolute number of new breast cancer
cases worldwide increased from
572,100 in 1980 to 1,050,346 for the
most recent period [3]. Comparison of
rates rather than absolute figures
excludes change attributable to ageing of
the population as well as differences in
age structures across countries. Even so,
most cancer registries of the world have
recorded an increase in the incidence of
breast cancer over the past 20 years
(Screening for breast cancer, p156). In the
period 1975-1990, the largest increases,
greater than 1% and sometimes 5% per
year, are exhibited by registries previously
having low rates of disease, mostly in Asia
and Africa, as well as in some parts of
Europe. In contrast, the smallest increases,
in general inferior to 0.5% per year, are
usually seen in places previously having
high rates, mostly in North America and
Europe. These changes are particularly
obvious in relation to disease in younger
women, that is below 45 years of age
[2,4]. However, mortality rates are falling,
probably due to better treatment (Fig.
5.19).
Etiology
Risk factors for breast cancer (Fig. 5.18)
specifically concern the reproductive life
of women. Increased risk is correlated
with early menarche, nulliparity or late age
at first birth, late menopause, as well as
hormonal factors, be they endogenous or
exogenous (e.g. long term use of oral contraceptives
or menopausal hormonal
replacement, Reproductive factors and
hormones, p76). Genetic risk factors are
discussed later (Pathology and genetics).
Other risk factors that may also be mediated
through a hormonal pathway include
obesity and diet, characterized by a high
caloric intake, not counterbalanced by sufficient
physical activity, high total and saturated
animal fat, as well as a diet poor in
fruits and vegetables and rich in meat and
alcohol [5,6]. The role of contaminants,
such as xenoestrogens and certain pesticides,
remains controversial. Radiation, in
Fig. 5.15 Fine needle aspirate of cells from a
breast tumour.
Fig. 5.16 An example of lobular carcinoma in situ,
comprising a well-differentiated malignant proliferation
without signs of invasion.
Fig. 5.17 Infiltrating ductal carcinoma. This is a
poorly-differentiated adenocarcinoma infiltrating
the adipose tissue.
particular at times of breast development,
causes breast cancer. Women with epithelial
proliferative lesions, particularly with
atypical ductal or lobular hyperplasia by
comparison with normal histology, have a
four to five times increase in the risk of
developing breast cancer [7].
Detection
The commonest presentation of breast
cancer is of a painless lump; other symptoms
may include dimpling of the overlying
skin, nipple inversion, oedema or peau
d’orange and blood-stained nipple discharge.
In countries where no mammo-
Breast cancer
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